The present invention generally relates to a sealing apparatus, and more particularly to a sealing apparatus for sealing a magnetic device such as a magnetic hard disk drive which has a base on which heat generating parts are mounted, a lid fitted onto the base and a sealing member between the base and the lid.
In a magnetic disk drive unit including a magnetic hard disk drive which uses a magnetic disk or hard disk as a data storage medium, a magnetic disk or hard disk within the magnetic disk drive and a driving mechanism of the magnetic disk drive unit is often damaged or any other operating problem takes place in the presence of dust, dirt or other foreign substances. Therefore, a sealing structure is required for preventing dust, dirt or other foreign substances from entering a driving mechanism inside the magnetic disk drive unit. FIG.1 shows an example of a conventional sealing apparatus which is provided for keeping the magnetic disk drive unit free from dust or foreign substances. In this conventional sealing apparatus shown in FIG. 1, a ring-like annular sealing member 2 is provided on an aluminum alloy base 1 made through aluminum die casting, and adheres to a circumferential edge 1a of the aluminum alloy base 1. Locating and adhering of this sealing member 2 on the aluminum alloy base 1 is made with a wall portion 1b which is elevated vertically from the circumferential edge 1a of the aluminum alloy base 1, as shown in FIG. 1. An aluminum alloy lid member 3 made through aluminum die casting has a downwardly extending peripheral portion 3a, and this peripheral portion 3a is placed in contact with the sealing member 2 and the lid member 3 is secured to the base 1 by a suitable fastener. The sealing member 2 is usually wider than a width of the peripheral portion 3a of the lid member 3. The external periphery of the lid member 3 at the peripheral edge 3a is substantially aligned with the external periphery of the sealing member 2 so that the sealing member 2 is pressed at its outermost periphery by the peripheral portion 3a of the lid member 3. In a case of the conventional sealing apparatus, the external periphery of the lid member 3 deviates from a centerline of the sealing member 2 which is located in the middle of a width of the sealing member 2, as shown in FIG. 1.
A disk drive motor (not shown in FIG. 1) for driving and rotating a magnetic disk within the magnetic disk drive and a head actuator (not shown in FIG. 1) for driving and swinging a head at a leading end of an arm in the magnetic disk drive are provided on the aluminum alloy base 1. During operation of the magnetic disk drive unit, the aluminum alloy base 1 is subject to heat owing to the running of the disk drive motor and the head actuator. Even if the base 1 and the lid member 3 are made of the same material with the same heat conductivity, heat from the moving parts such as the disk drive motor and the head actuator is conducted fast to the aluminum alloy base 1, but the heat is not transmitted directly to the lid member 3. The base 1 accordingly exhibits a relatively great thermal expansion when compared with that of the lid member 3. At the same time, an adhesive layer which is formed to join the sealing member 2 to the aluminum alloy base 1 gradually softens due to heat generated from the disk drive motor and the head actuator through the base 1, causing an undesired separation of the sealing member from the aluminum alloy base 1.
As described above, the sealing member 2 is pressed at its external periphery on the aluminum alloy base 1 by the lid member 3 and a differential thermal expansion is produced between the base 1 and the lid member 3 during operation of the magnetic disk drive unit. A slanting direction force F as indicated in FIG. 1 acts on the sealing member 2 so as to move the sealing member 2 toward the inside of the magnetic disk drive unit with respect to the aluminum alloy base 1. When the magnetic disk drive unit is in operation, the rates, the sealing member 2 is likely to deviate from the base 1 toward the inside of the magnetic disk drive unit. And, when the magnetic disk drive unit stops the operation, the adhesive layer of the sealing member 2 hardens due to a drop of temperature of the aluminum alloy base 1, thereby the sealing member 2 being moved to a position where the sealing member 2 deviates from the original position on the base 1. Therefore, in a case of the conventional sealing structure described above in which the magnetic disk drive is sealed, there is a problem in that the sealing member 2 is likely to deviate from the original position toward the inside of the magnetic disk drive unit little by little due to repetitious operations and stopping of the magnetic disk drive unit, so that the sealing member 2 is finally separate from the base 1, thus the sealing apparatus no longer having a sealing function to keep the magnetic disk drive unit free from dust or foreign matter.